1. Field of the Invention
The present invention relates to a transmission module, a reception module, a transmission method, a reception method, and a communication system.
Priority is claimed on Japanese Patent Application No. 2010-022225, filed Feb. 3, 2010, the content of which is incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
Since Picture Transfer Protocol: ISO/DIS 15740 (hereinafter PTP) can be applied without transport layer dependency, in Universal Serial Bus (USB), USB Still Image Capture Device Class (hereinafter SICD) has been standardized, while in IP networks, CIPA DC-005 “Picture transfer protocol” over TCP/IP networks (hereinafter PTP-IP) has been standardized. Various communications means, both wired and wireless, have recently been developed, and application of PTP is expected to proliferate in the future.
When applying PTP in each transport layer, it must be implemented in accordance with the characteristics of each transport layer. Since cancellation of PTP operation sometimes entails a halt of data transfer, implementation is different for each transport. A method of cancelling a PTP operation when the transport layer is USB (SICD) is as follows.
When the initiator cancels:
Step 1: The initiator halts data transfer (transmission/reception) by halting the issue of USB tokens (in/out tokens).
Step 2: The initiator issues a USB class-specific Cancel Request, and requests cancellation of the PTP operation.
Step 3: The responder cancels the PTP operation being executed.
When the responder cancels:
Step 1: The responder halts data transfer by stalling the bulk-in/out endpoint.
Step 2: The initiator cancels the PTP operation.
In USB, the USB host, namely the initiator, has control rights over all data transfers, and performs transmission/reception of data by using USB tokens (in/out tokens etc.) to poll whether data transfer is possible to the USB device, namely the responder. The responder (USB device) has a halt function of halting data currently being transferred by returning a stall to the USB token issued by the initiator (USB host). A USB specification is disclosed in “Universal Serial Bus Revision 2.0 specification”, (http://www.usb.org/developers/docs/).